lsst.sphgeom._continue_class.Region Class Reference

Public Member Functions
Region	from_ivoa_pos (cls, str pos)
str	to_ivoa_pos (self)

Detailed Description

A minimal interface for 2-dimensional regions on the unit sphere.

Definition at line 101 of file _continue_class.py.

Member Function Documentation

from_ivoa_pos()

Region lsst.sphgeom._continue_class.Region.from_ivoa_pos	(		cls,
		str	pos )

Create a Region from an IVOA POS string.

Parameters
----------
pos : `str`
    A string using the IVOA SIAv2 POS syntax.

Returns
-------
region : `Region`
    A region equivalent to the POS string.

Notes
-----
See
https://ivoa.net/documents/SIA/20151223/REC-SIA-2.0-20151223.html#toc12
for a description of the POS parameter but in summary the options are:

* ``CIRCLE <longitude> <latitude> <radius>``
* ``RANGE <longitude1> <longitude2> <latitude1> <latitude2>``
* ``POLYGON <longitude1> <latitude1> ... (at least 3 pairs)``

Units are degrees in all coordinates.

Definition at line 105 of file _continue_class.py.

    def from_ivoa_pos(cls, pos: str) -> Region:
        """Create a Region from an IVOA POS string.
 
        Parameters
        ----------
        pos : `str`
            A string using the IVOA SIAv2 POS syntax.
 
        Returns
        -------
        region : `Region`
            A region equivalent to the POS string.
 
        Notes
        -----
        See
        https://ivoa.net/documents/SIA/20151223/REC-SIA-2.0-20151223.html#toc12
        for a description of the POS parameter but in summary the options are:
 
        * ``CIRCLE <longitude> <latitude> <radius>``
        * ``RANGE <longitude1> <longitude2> <latitude1> <latitude2>``
        * ``POLYGON <longitude1> <latitude1> ... (at least 3 pairs)``
 
        Units are degrees in all coordinates.
        """
        shape, *coordinates = pos.split()
        coordinates = tuple(float(c) for c in coordinates)
        n_floats = len(coordinates)
        if shape == "CIRCLE":
            if n_floats != 3:
                raise ValueError(f"CIRCLE requires 3 numbers but got {n_floats} in '{pos}'.")
            center = LonLat.fromDegrees(coordinates[0], coordinates[1])
            radius = Angle.fromDegrees(coordinates[2])
            return Circle(UnitVector3d(center), radius)
 
        if shape == "RANGE":
            if n_floats != 4:
                raise ValueError(f"RANGE requires 4 numbers but got {n_floats} in '{pos}'.")
            # POS allows +Inf and -Inf in ranges. These are not allowed by
            # Box and so must be converted.
            return Box(
                LonLat.fromDegrees(_inf_to_lon(coordinates[0]), _inf_to_lat(coordinates[2])),
                LonLat.fromDegrees(_inf_to_lon(coordinates[1]), _inf_to_lat(coordinates[3])),
            )
 
        if shape == "POLYGON":
            if n_floats % 2 != 0:
                raise ValueError(f"POLYGON requires even number of floats but got {n_floats} in '{pos}'.")
            if n_floats < 6:
                raise ValueError(
                    f"POLYGON specification requires at least 3 coordinates, got {n_floats // 2} in '{pos}'"
                )
            # Coordinates are x1, y1, x2, y2, x3, y3...
            # Get pairs by skipping every other value.
            pairs = list(zip(coordinates[0::2], coordinates[1::2], strict=True))
            vertices = [LonLat.fromDegrees(lon, lat) for lon, lat in pairs]
            return ConvexPolygon([UnitVector3d(c) for c in vertices])
 
        raise ValueError(f"Unrecognized shape in POS string '{pos}'")
 

to_ivoa_pos()

str lsst.sphgeom._continue_class.Region.to_ivoa_pos

(

self

)

Represent the region as an IVOA POS string.

Returns
-------
pos : `str`
    The region in ``POS`` format.

Definition at line 165 of file _continue_class.py.

    def to_ivoa_pos(self) -> str:
        """Represent the region as an IVOA POS string.
 
        Returns
        -------
        pos : `str`
            The region in ``POS`` format.
        """
        raise NotImplementedError("This region can not be converted to an IVOA POS string.")
 
 
@_continueClass

---

The documentation for this class was generated from the following file:

• /j/snowflake/release/lsstsw/stack/lsst-scipipe-10.1.0/Linux/sphgeom/gf9a733ac38+8c5ae1fdc5/python/lsst/sphgeom/_continue_class.py